How to connect to a serial / COM port from your browser with HyperTerminal online

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HyperTerminal online - web serial terminal screenshot

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A step-by-step guide to talking to a serial device with HyperTerminal online - no install, no account. (Background and tech details in the original post.)

What you need

  • Chrome or Edge on desktop (the Web Serial API is not in Firefox/Safari)
  • A serial device on a COM port or USB-serial adapter - CH340, CP210x, FTDI, PL2303 and friends all work

Steps

  1. Open https://www.clearevo.com/hyperterminal/
  2. Click Call and pick your COM port / USB-serial adapter from the browser’s port list.
  3. Set the line parameters in File > Properties: bits per second, data bits, parity, stop bits, flow control. The status bar shows the current setting, e.g. 115200 8-N-1, plus a connect timer.
  4. Type away. ASCII Setup has local echo and CR/LF options if your device expects them.
  5. To log the session, use Capture Text - it saves everything received to a .txt file. Send Text File pushes a file out the port line by line.

No hardware handy?

Under File > Properties > “Connect using” there are three clearly-marked DEMO simulated devices (not real hardware): an AT-command modem (try AT, ATI, AT+CSQ, AT+HELP), and two GNSS receivers streaming valid NMEA. The demos work in any browser, Firefox and Safari included.

Everything runs client-side - your data never leaves your machine (Google Analytics for visit stats only).

This tool is free software and open source: ykasidit/hyperterminal - issues and pull requests welcome.

Full disclosure: this post - and any code or tool it describes - was co-authored with Claude (Anthropic’s AI, via Claude Code). I directed, guided and reviewed. I don’t want to pretend otherwise.

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